The AVK directory does list the trojan but there is nothing in the Quarantine File!

Does anyone know what this trojan does or how dangerious it is? How can I get rid of it? In Safe Mode I ran AVK, Microsoft Antispyware, and Spy Sweeper. I also looked for it in the event viewer. None of these found or blocked it. Neither did Zone Alarm, Trojan Hunter or Spyware Blaster. I keep all my windows updates current as well as the rest of my protection. I use Firefox for everything (except Windows Update). My only symptom so far is that my Host File was almost hijacked. I blocked it with the Microsoft Antispyware program.

A computer knowlegable friend I spoke to at work said that by using System Restore (Windows XP) I can restore my computer to before It was infected by the trojan and that would fix the problem. I have not done that yet because I would have to reinstall a lot of programs and updates, and so far I have not had any symptoms from the trojan. I am not even actually sure wheather or not I am infected- I have Gdata AVK antivirus program, and the first time that it's KAV monitor found the trojan the log said that it quarintined it. It did log it but it was not listed in the quarintine file. Two other times the log said that it found and quarintined it, and this time it did list both in the quarintine file. Two other times it said that it found it but did not clean, delete, or quarintine it. My friend at work said that this virus only effects Explorer, and that it would only be activated by going to certain web sites (probably adult.) I use Firefox. He says that as long as I'm using Firefox I am not going to be affected. The only time I use Explorer is for Windows Updates, and I also ran a few on-line virus scanners with Explorer. Execpt for the first time, the other times I purposely went to a few web sites that I thought might be responsible for the trojan (I must be nuts!) to see how my anti virus handled it. I do not know why it said it quarintined it once but apparently did not, sometimes did quarintine it, and other times did nothing with it.

Like I said, so far I have not had any symptoms from the trojan. If you or anyone knows how to find out if my computer is actually infected or not, and how to get rid of it, I sure would appreciate it. Also, should I really do a System Restore, or not?

Thanks for the ino. It looks like I have been woring for nothing. I did another scan in safe mode with both AVK and Trojan Hunter and came up clean. Now I can find something else to worry and obsess about.